Paper Number
GN25                         My Program 

Session
Self-assemblies, Gels and Networks

Title
Granular hydrogels as brittle yield stress fluids

Presentation Date and Time
October 21, 2025 (Tuesday) 1:50

Track / Room
Track 2 / Sweeney Ballroom B

Authors (Click on name to view author profile)

  1. Lee, Jiye (University of Illinois Urbana-Champaign)
  2. Thompson, Gunnar B. (University of Illinois Urbana-Champaign)
  3. Kamani, Krutarth M. (University of Illinois Urbana-Champaign)
  4. Flores-Velasco, Noah (University of Illinois Urbana-Champaign)
  5. Rogers, Simon A. (University of Illinois Urbana-Champaign, Chemical and Biomolecular Engineering)
  6. Harley, Brendan A. (University of Illinois Urbana-Champaign)

Author and Affiliation Lines (in printed abstract book)
Jiye Lee, Gunnar B. Thompson, Krutarth M. Kamani, Noah Flores-Velasco, Simon A. Rogers and Brendan A. Harley
University of Illinois Urbana-Champaign, Urbana, IL 61801

Speaker / Presenter 
Lee, Jiye

Keywords
experimental methods; theoretical methods; biomaterials; gels; granular materials; networks; non-Newtonian fluids; particualte systems

Text of Abstract
While granular hydrogels are increasingly used in biomedical applications, methods to capture their rheological behavior generally consider shear-thinning and self-healing properties or produce ensemble metrics such as the dynamic moduli while neglecting transient yielding and unyielding processes. Combining oscillatory shear testing with Brittility (Bt) via the Kamani-Donley-Rogers (KDR) model, we show that granular hydrogels behave as brittle yield stress fluids. We quantify steady and transient rheology as a function of microgel properties and granular composition for polyethylene glycol and gelatin microgels. The KDR model with Bt captures granular hydrogel behavior for a wide range of design parameters, reducing the complex rheology to a determination of model parameters. In granular mixtures, we observed monotonic dependencies of the elastic modulus, structural viscosity, and brittility upon granular composition, while the yield stress was lower for mixtures. Microgel size distribution and polymer fraction were the most influential parameters in monolithic granular hydrogels, while microgel size and packing density were less impactful. The model robustly captures self-healing behavior and reveals that granular hydrogel relaxation accelerates with an increased small-amplitude strain rate. This quantitative framework is an important step toward rational design of granular hydrogels for applications ranging from injection and in situ stabilization to 3D bioprinting.